6. _Panicle._--A compound raceme--a raceme the pedicels of which are themselves branched. 7. _Capitulum_ or _Flower-head_.--A dense cluster of flowers, all attached to a common broad disc or receptacle. Other forms of inflorescence may also be compound. Thus, a _compound umbel_ is produced when the pedicels of an umbel are themselves umbellate. THE FLOWER A flower, if complete in all its parts, consists of modified leaves arranged in four distinct whorls, the parts being directly or indirectly attached to a receptacle. The outer whorl is the _calyx_, and is composed of parts called _sepals_, which may be either united or distinct. The calyx is usually green; but, in some cases, is more or less highly coloured. Sometimes the calyx is quite free from the pistil or central part of the flower, the sides of which are thus left naked, and the calyx is then said to be _inferior_. If, however, it is united to the surface of the pistil it is _superior_. When it remains after other parts of the flower have decayed, it is said to be _persistent_. The second whorl--the _corolla_--is usually the whorl that gives most beauty to the flower. It is composed of parts, united or distinct, called _petals_. Both calyx and corolla vary very considerably in shape. They may be cup-shaped, tubular, bell-shaped, spreading, funnel-shaped, lipped, &c. If the sepals and petals are arranged symmetrically round a common centre, the calyx and corolla, respectively, are said to be _regular_; if otherwise, they are _irregular_. The third whorl consists of the _stamens_, each of which, in its most perfect form, is made up of a _filament_ or stalk, and an _anther_ which, when mature, splits and sets free the _pollen_ that is formed within it. Sometimes the stamen has no filament, and the anther is then said to be sessile. The mode of attachment of the stamens is very variable. They may grow from immediately below the pistil, or from its summit; or they may be attached to either the petals or the sepals. The filaments are usually distinct, but sometimes they are united in such a manner as to form a tube, or grow into two or more bundles. The anthers are usually distinct, even when the filaments are united; but these sometimes grow together. [Illustration: LONGITUDINAL SECTION THROUGH THE FLOWER OF THE BUTTERCUP Showing the calyx, corolla, stamens, and pistil. The pistil consists of several distinct carpels, one of which is represented in section to show its single ovule.]